Method And Device For On-line Ultrasonic Measurement Of Wall Thickness Of Complex Structural Parts

The wall thickness of aircraft complex structural parts is an important inspection index of machining quality,which plays an important role in ensuring the strength and stiffness of aircraft structural parts.At present,the measurement of the wall thickness of aircraft structural parts is mainly manual measurement and CMM measurement.Manual measurement is low in efficiency,and CMM has the problem of secondary positioning error,so it is difficult to adapt to the detection of the intermediate machining state,and the existing online automatic measurement method is difficult to adapt to the complex working conditions in CNC machining.In view of the above problems,this thesis conducts in-depth research on non-contact ultrasonic thickness measurement technology,and the main research contents are as follows:(1)A non-contact on-line water-coupled ultrasonic thickness measuring device is designed.In the on-line non-contact water coupling ultrasonic thickness measurement environment,the initial water flow is in the turbulent non-columnar state and contains bubbles,which brings great challenges to ultrasonic thickness measurement.Aiming at the above problems,the columnar continuity equation of laminar flow is established,the realization method of columnar laminar flow based on shunt control is proposed,the structure of non-contact thickness measuring device and the hardware circuit of ultrasonic transmitting and receiving are designed.(2)The ultrasonic signal denoising method based on wavelet transform is studied.Aiming at the problem that there is much noise in the echo signal of non-contact ultrasonic thickness measurement,the wavelet transform is adopted to remove the noise in the echo signal,and the noise removal effect of different wavelet functions,decomposition layers and threshold methods is studied.(3)The ultrasonic thickness measurement path planning method considering the local rigidity of complex structural parts is studied.In view of the existing methods to generate testing points is hard to realize non-contact online high-efficiency ultrasonic thickness measurement,partial rigidity of parts' evaluation standard is established,studies the method of measurement points automatically generated and the method of ultrasonic thickness measurement path planning,so as to realize the non-contact online thickness measurement of the complex structural parts.(4)Based on the above research,a non-contact ultrasonic thickness measurement system is developed,and corresponding experiments are designed for verification.The experimental results show that the ultrasonic thickness measurement system can realize the online non-contact thickness measurement of complex structural parts.